Impeller for fuel pump and fuel pump in which the impeller is employed

ABSTRACT

An impeller is employed for a fuel pump and boosts a pressure of fuel by rotating the fuel in a pump passage formed in the fuel pump in a rotational direction of the impeller. The impeller includes a plurality of vane grooves formed adjacent to each other in the rotational direction of the impeller and a plurality of vanes formed adjacent to each other in the rotational direction. Each one of the plurality of vanes divides one of adjacent two of the plurality of vane grooves from the other. A difference between a maximal value and a minimum value of an adjacent vane angle is set in a range of 2.5° to 4°. A fuel pump includes a motor unit, the impeller, and a casing member. The impeller is rotated by rotation driving force of the motor unit. The casing member rotatably receives the impeller and defines the pump passage.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2006-95335 filed on Mar. 30, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an impeller for a fuel pump and a fuel pump in which the impeller is employed.

2. Description of Related Art

In a conventional fuel pump, a plurality of vane grooves is formed on a disklike impeller in its rotational direction, and a vane divides vane grooves that are adjacent to each other in a rotational direction of the impeller. By rotating the impeller, a pressure of fuel in a pump passage formed along the vane grooves is boosted (e.g., JP11-50990A corresponding to U.S. Pat. No. 5,975,843). In such a fuel pump, if vanes adjacent to each other in the rotational direction of the impeller are arranged at equiangular intervals, a noise having a high peak of a sound pressure at a frequency that corresponds to (a sum of vanes)×(a rotational speed of the impeller) is generated (FIG. 8A) when the impeller rotates.

In JP11-50990A, the vane grooves (vanes) are arranged such that at least a part of angles (adjacent vane angles), which the vanes adjacent to each other in the rotational direction of the impeller make, are different. As a result, a range of frequencies, at which the sound pressure has its peak, is broadened, and the peak of the sound pressure is reduced (FIG. 8B).

When the impeller rotates, fuel flows repeatedly from a forward vane groove into a backward vane groove in the rotational direction of the impeller, and thereby the impeller boosts the pressure of fuel by turning the fuel into a swirling flow. In a configuration of the impeller that boosts the pressure of fuel in such a manner, when a difference between two adjacent vane angles is large and thus a difference between two widths of the vane grooves divided by the vanes in the rotational direction of the impeller is large, a difference between an amount of fuel flowing into the vane groove and an amount of fuel flowing out of the vane groove is large. Consequently, the pressure of fuel cannot be boosted sufficiently in a pump unit of the fuel pump, which boosts the pressure of fuel by turning the fuel into the swirling flow. As a result, efficiency of the pump unit in boosting the pressure decreases, pump efficiency of the pump unit decreases. When the adjacent vane angles are the same, and thus the widths of the vane grooves in the rotational direction of the impeller are the same, the pump efficiency of the pump unit increases. Nevertheless, as described above, the peak of the sound pressure of the noise generated by the rotating of the impeller becomes high.

Efficiency of the fuel pump is expressed by (motor efficiency)×(pump efficiency). Therefore, when the pump efficiency is improved, the efficiency of the fuel pump is improved. Given I (a driving current supplied to a motor unit of the fuel pump), V (an applied voltage), T (torque in the motor unit), N (a rotational speed of the motor unit), P (a pressure of fuel discharged by the fuel pump), and Q (a fuel discharge rate), the motor efficiency is expressed by (motor efficiency)=(T×N)/(I×V), and the pump efficiency is expressed by (pump efficiency)=(P×Q)/(T×N). Thus, the efficiency of the fuel pump is expressed by (efficiency of the fuel pump)=(motor efficiency)×(pump efficiency)=(P×Q)/(I×V).

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide an impeller for a fuel pump. The impeller reduces a peak of a sound pressure of a noise and restricts a decrease in pump efficiency. Furthermore, it is another objective to provide a fuel pump that employs the impeller.

To achieve the objective of the present invention, there is provided an impeller that is employed for a fuel pump and boosts a pressure of fuel by rotating the fuel in a pump passage, which is formed in the fuel pump in a rotational direction of the impeller. The impeller includes a plurality of vane grooves and a plurality of vanes. The plurality of vane grooves is formed adjacent to each other in the rotational direction of the impeller. The plurality of vanes is formed adjacent to each other in the rotational direction of the impeller. Each one of the plurality of vanes divides one of adjacent two of the plurality of vane grooves from the other. A difference between a maximal value and a minimum value of an adjacent vane angle is set in a range of 2.5° to 4°. The adjacent vane angle is an angle, which is made around a rotational axis of the impeller between respective ends of adjacent two of the plurality of vanes in the rotational direction of the impeller.

To achieve the objective of the present invention, there is also provided a fuel pump including a motor unit, the impeller, and a casing member. The impeller is rotated by rotation driving force of the motor unit. The casing member rotatably receives the impeller and defines the pump passage.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1A is an overall view of an impeller viewed from a fuel inlet side according to according to a first embodiment of the present invention;

FIG. 1B is an enlarged view of an area near vane grooves shown in FIG. 1A;

FIG. 2 is a cross-sectional view of a fuel pump according to the first embodiment;

FIG. 3A is a schematic view of the vane grooves of the impeller viewed from the fuel inlet side according to the first embodiment;

FIG. 3B is a cross-sectional view taken along a line IIIB-IIIB in FIG. 3A;

FIG. 4 is an enlarged view of pump passages shown in FIG. 2;

FIG. 5 is a graph showing a relationship between a dispersion range and a peak of a sound pressure and a relationship between the dispersion range and pump efficiency;

FIG. 6 is a graph showing a relationship between an adjacent vane angle and the pump efficiency;

FIG. 7 is an overall view of an impeller viewed from a fuel inlet side according to a second embodiment of the present invention;

FIG. 8A is a graph showing the peak of the sound pressure of vanes at regular intervals; and

FIG. 8B is a graph showing the peak of the sound pressure of vanes at irregular intervals.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described with reference to drawings.

First Embodiment

FIG. 2 shows a fuel pump 10, in which an impeller 30 according to a first embodiment of the present invention is employed. The fuel pump 10 is, for example, an in-tank turbine pump, which is attached to an inside of a fuel tank of a vehicle or the like. The fuel pump 10 supplies fuel in the fuel tank to a fuel injection valve (not shown). The fuel pump 10 is set such that its discharge pressure includes a range of 0.25 to 1 [Mpa], its discharge rate includes a range of 50 to 250 [L/h], and its rotational speed includes a range of 4000 to 12000 [rpm].

The fuel pump 10 includes a pump unit 12 and a motor unit 13, which drives the pump unit 12 to rotate. A housing 14 is for the pump unit 12 and the motor unit 13, and caulks an end cover 16 and a pump case 20.

The pump unit 12 is a turbine pump, which has the pump case 20, a pump case 22 and the impeller 30. The pump case 22 is press-fitted into the housing 14, and is pressed on a stage part 15 of the housing 14 in an axial direction of the impeller 30. The pump cases 20, 22 are casing members that rotatably receive the impeller 30 as a rotating member. C-shaped pump passages 202 are formed respectively, between the pump cases 20, 22 and the impeller 30.

As shown in FIGS. 1A, 1B, a plurality of vane grooves 36 is formed on an outer circumferential part of the impeller 30 in a rotational direction of the impeller 30, which is formed in a disk-shaped manner. Widths of the vane grooves 36 in a circumferential direction of the impeller 30 are uneven. As a result, the vane grooves 36 are arranged with an irregular pitch in the rotational direction of the impeller 30. Two vane grooves 36 adjacent to each other in the rotational direction are divided by a vane 34. When the impeller 30 rotates together with a shaft 51 in accordance with rotation of an armature 50 shown in FIG. 2, fuel flows from a radially outer side of the vane groove 36, which is located forward in the rotational direction, into the pump passages 202, and flows into a radially inner side of the vane groove 36, which is located backward in the rotational direction. Since fuel repeatedly flows from and into the vane grooves 36 in this manner many times, fuel is turned into a swirling flow 220 (FIG. 4) and its pressure is boosted in the pump passages 202 shown in FIG. 2. When the impeller 30 rotates, fuel is drawn from an inlet (not shown) placed at the pump case 20 and its pressure is boosted in the pump passages 202 by the rotating of the impeller 30. Then, the fuel is sent from an outlet (not shown) placed at the pump case 22 to a motor unit 13 side with pressure applied, and passes through a fuel passage 206 between a permanent magnet 40 and the armature 50. After this, the fuel is supplied from an outlet 210 provided in the end cover 16 to an engine side. An air vent hole 204 provided in the pump case 20 is for discharging air included in fuel in the pump passages 202 into the outside of the fuel pump 10.

The four permanent magnets 40, which have different magnetic poles from each other in a rotational direction of the armature 50, are formed like an arc of a quarter circle and placed on an inner circumferential wall of the housing 14 in a circumferential manner.

By covering an end part of the armature 50 on an impeller 30 side with a resin cover 70, rotational resistance of the armature 50 is reduced. A commutator 80 is joined to the other end part of the armature 50. The shaft 51 as a rotational axis of the armature 50 is held by bearing members 24, which are received and supported by the end cover 16 and the pump case 20 respectively.

The armature 50 has a central core 52 around the shaft 51. The shaft 51 is press-fitted into the cylindrically formed central core 52, which has a hexagonal shape on its cross-sectional surface. Six magnetic pole cores 54 are arranged around the central core 52 in the rotational direction of the armature 50, and are fitted together with the central core 52. A bobbin 60 made of dielectric resin is fitted into the periphery of the magnetic pole cores 54, and coils 62 are formed by concentratedly winding a winding around the periphery of the bobbin 60.

An end part of each coil 62 on a commutator 80 side is electrically connected to a coil terminal 64. The coil terminal 64 corresponds to a position of each coil 62 in the rotational direction of the armature 50, and is fitted with a terminal 84 on the commutator 80 side to form electrical connection. The other end part of the coil 62 on the impeller 30 side is electrically connected to a coil terminal 66. Six coil terminals 66 are electrically connected by an annular terminal 68.

The cassette-type commutator 80 is integrally formed. When the shaft 51 is inserted into a through hole 81 of the commutator 80 with the shaft 51 press-fitted into the central core 52 to join the commutator 80 to the armature 50, each terminal 84 of the commutator 80, which projects to a armature 50 side, is fitted into the corresponding coil terminal 64 of the armature 50 to be electrically connected to the coil terminal 64.

The commutator 80 has six segments 82, which are arranged in the rotational direction of the armature 50. The segment 82 is formed from carbon, for example, and the segments 82 are electrically insulated from each other by a gap and a dielectric resin member 86.

Each segment 82 is electrically connected to the terminal 84 via an intermediate terminal 83. The dielectric resin member 86 integrates the segments 82 (except a surface on which a brush (not shown) slides), the intermediate terminal 83, and the terminal 84 by insert molding, thereby constituting the commutator 80. When the commutator 80 rotates together with the armature 50, each segment 82 contacts the brush in turn. When the commutator 80 contacts the brush in turn while rotating, an electric current supplied to the coil 62 is rectified. The permanent magnet 40, the armature 50, the commutator 80, and the brush (not shown) constitute a direct-current motor.

(Impeller 30)

A configuration of the impeller 30 will be described in further detail.

The impeller 30 is integrally formed from resin in a disk-shaped manner. As shown in FIGS. 1A, 1B, an outer circumference of the impeller 30 is surrounded by an annular part 32, and the vane grooves 36 are formed on an inner circumferential side of the annular part 32. As shown in FIG. 3B, two vane grooves 36 adjacent to each other in the rotational direction of the impeller 30 are divided by the V-shaped vane 34, which is inclined forward in the rotational direction from a generally central part of the impeller 30 in a thickness direction of the impeller 30 to both end surfaces 31 of the impeller 30 in the thickness direction. As shown in FIG. 4, although a radially inner part of the vane groove 36 is divided by a dividing wall 35, which projects from a radially inner part into a radially outer part of the vane groove 36, the vane groove 36 penetrates through a radially outer side away from the dividing wall 35 in a direction of a rotational axis of the impeller 30. Fuel, which flows from the pump passages 202 on both sides of the impeller 30 in the direction of the rotational axis of the impeller 30 into the vane groove 36, is turned by the dividing wall 35 into two swirling flows 220 that rotates in an opposite direction to each other on both sides of the impeller 30 in the direction of the rotational axis of the impeller 30.

As shown in FIGS. 3A, 3B, at least a radially inner side part of a backward surface 37 of the vane groove 36, which is located backward in the rotational direction of the impeller 30, is inclined from a radially inner side to a radially outer side (i.e., backward in the rotational direction). A line segment 110 between a radially inner end 37 a and a radially outer end 37 b of the backward surface 37 is inclined backward in the rotational direction as the line segment 110 extends toward the radially outer side, relative to a line 104, which extends radially outward from the radially inner end 37 a on a radius 102 of the impeller 30. That is, the backward surface 37 is inclined backward in the rotational direction as it extends radially outward. In FIG. 3A, a numeral 100 indicates a rotational axis of the impeller 30. The radially inner end 37 a and the radially outer end 37 b of the backward surface 37 of the vane groove 36 coincide with one end part of the vane 34 in the rotational direction, more specifically in the first embodiment, a radially inner end 34 a and a radially outer end 34 b at this one end part, which is located forward in the rotational direction, respectively.

As shown in FIGS. 1A, 1B, between two vanes 34 adjacent to each other in the rotational direction of the impeller 30, given an angle (adjacent vane angle) θ that two lines 104 passing through the corresponding radially outer end 34 b, which is one end of the vane 34 in the rotational direction, and the rotational axis 100, make with each other, a dispersion range (θ_(max)-θ_(min)), which is a difference between a maximal value θ_(max) and a minimum value θ_(min) of the adjacent vane angle θ, is set to be in a range of 2.5°≦dispersion range≦4°.

When the impeller 30 rotates, a noise having a high peak of a sound pressure at a frequency that corresponds to (a sum of the vanes 34)×(a rotational speed of the impeller 30) is generated if the adjacent vane angles θ of the vanes 34 are the same (FIG. 8A). When the dispersion range of the adjacent vane angles θ of the vanes 34 is small, a range of frequencies, at which the sound pressure has its peak, is not broadened, and thus the peak of the sound pressure cannot be reduced as in the case where the adjacent vane angles θ are the same. Nevertheless, when the dispersion range of the adjacent vane angles θ of the vanes 34 is small, a difference between an amount of fuel flowing into the vane groove 36 and an amount of fuel flowing out of the vane groove 36 is small. As a result, when the impeller 30 rotates, fuel repeatedly flows into and out of the vane groove 36, and efficiency in boosting the pressure of fuel increases. Therefore, pump efficiency of the pump unit 12 and efficiency of the fuel pump 10 increase.

When the dispersion range of the adjacent vane angles θ of the vanes 34 is large, on the other hand, the range of frequencies, at which the sound pressure has its peak, spreads out, thereby reducing the peak of the sound pressure (FIG. 8B). However, when the dispersion range of the adjacent vane angles θ is large, the difference between the amount of fuel flowing into the vane groove 36 and the amount of fuel flowing out of the vane groove 36 is large. Accordingly, when the impeller 30 rotates, fuel repeatedly flows into and out of the vane groove 36, and the efficiency of the pump unit 12 in boosting the pressure of fuel decreases. Hence, the pump efficiency of the pump unit 12 and the efficiency of the fuel pump 10 decrease.

FIG. 5 shows relationships between the dispersion range and, the peak of the sound pressure as well as the pump efficiency. A line graph 300 indicates a relationship between the dispersion range and the peak of the sound pressure, and a line graph 302 indicates a relationship between the dispersion range and the pump efficiency. As can be seen from characteristics in FIG. 5, when the peak of the sound pressure is equal to or smaller than 135 [dB], and a decrease in the pump efficiency is equal to or smaller than 1% compared to an optimal value of the pump efficiency when all of the adjacent vane angles θ of the vanes 34 are the same (i.e., the dispersion range: 0°), the dispersion range falls within the range of 2.5°≦dispersion range≦4°. In this manner, by setting the dispersion range in the range of 2.5°≦dispersion range≦4°, the peak of the sound pressure can be reduced, and the decrease in the pump efficiency can be restricted.

As a curve 310 in FIG. 6 shows, not only the dispersion range but a magnitude of the adjacent vane angle itself influences the pump efficiency. FIG. 6 shows a relationship between the adjacent vane angle θ and the pump efficiency when all of the adjacent vane angles θ of the vanes 34 of the impeller 30 are the same.

When the adjacent vane angle is smaller than 8° (θ<8°), a width of the vane groove 36 in the rotational direction of the impeller 30 is small, thereby decreasing volume. Thus, fuel, which is turned into the swirling flow 220, cannot flow into the vane groove 36 sufficiently. Accordingly, increasing energy of the swirling flow 220 is difficult. When the adjacent vane angle is larger than 12° (θ>12°), the width of the vane groove 36 in the rotational direction is large, thereby increasing volume. Thus, it is difficult to flow out the fuel, which flows into the vane groove 36, as the swirling flow 220 and to increase the energy of the swirling flow 220. When the energy of the swirling flow 220 does not increase, the efficiency in boosting the pressure of fuel decreases, so that the pump efficiency decreases.

As compared to this, in the impeller 30, in which all of the adjacent vane angles θ of the vanes 34 are the same, when the adjacent vane angle θ is set in a range of 8°≦adjacent vane angle θ≦12°, the decrease in the pump efficiency from its optimal value is equal to or smaller than 1% (FIG. 6). Therefore, even when the adjacent vane angles θ of the vanes 34 are set to be irregular in the first embodiment, by setting the irregular adjacent vane angles θ in a range of 8°≦adjacent vane angle≦12° respectively, the decrease in the pump efficiency from its optimal value is equal to or smaller than 1% in the range of 2.5°≦dispersion range≦4°.

As described thus far, in the first embodiment, by setting the dispersion range of the irregular adjacent vane angles θ of the vanes 34, which are adjacent to each other in the rotational direction of the impeller 30, in the range of 2.5°≦dispersion range≦4°, the peak of the sound pressure of the noise, which is generated by the rotating of the impeller 30, can be reduced, and the decrease in the pump efficiency of the pump unit 12 of the fuel pump 10 can be restricted as much as possible.

Moreover, in the first embodiment, a radially outer part of the vane grooves 36 is surrounded by the annular part 32, so that the pump passage 202 is not formed on an outer circumferential side of the impeller 30. As a result, a pressure difference (in the rotational direction) of fuel, the pressure of which is boosted in the pump passage 202, is not directly applied to a radial direction of the impeller 30, and thus force applied to the impeller 30 radially decreases. Consequently, misalignment of the rotational axis of the impeller 30 can be restricted, and thereby the impeller 30 can rotate smoothly.

Second Embodiment

FIG. 7 shows a second embodiment of the present invention. The same numerals are used to indicate substantially the same components as the first embodiment described above. In the second embodiment, a configuration of a fuel pump, in which an impeller 90 is employed, is substantially the same as the first embodiment.

In the impeller 30 of the first embodiment, the radially outer part of the vane grooves 36 is surrounded by the annular part 32. In the impeller 90 of the second embodiment, on the other hand, radially outer parts of vane grooves 92 is open. Two vane grooves 92 adjacent to each other in a rotational direction of the impeller 90 are divided by a vane 94.

In the second embodiment as well, adjacent vane angles θ of the vanes 94 and their dispersion range are set in a range of 8°≦adjacent vane angle≦12°, and 2.5°≦dispersion range≦4°, respectively.

Other Embodiments

Although the dispersion range and the adjacent vane angle θ are set in the range of 2.5°≦dispersion range≦4°, and 8°≦adjacent vane angle≦12°, respectively in the above embodiments, as long as the dispersion range is in the range of 2.5°≦dispersion range≦4°, the adjacent vane angle θ may not be set in the range of 8°≦adjacent vane angle≦12°.

Additionally, in the above embodiments, the V-shaped vane is formed such that it is inclined forward in the rotational direction of the impeller from the central part of the impeller in the thickness direction of the impeller toward both end surfaces of the impeller in the thickness direction. Also, the backward surface of the vane groove (backward surface 37 in the first embodiment) is inclined backward in the rotational direction as it extends in a radially outward direction. However, as long as the dispersion range is set in the range of 2.5°≦dispersion range≦4°, shapes of the vane and the vane groove may not be limited to those described in the above embodiments. For example, the vane may be formed like a flat plate in the thickness direction of the impeller, and the backward surface of the vane groove may have a shape that extends along the radial direction of the impeller.

Besides, in the above embodiments, a brush motor is employed as the motor unit of the fuel pump. Alternatively, a brushless motor may be employed for the motor unit.

In this manner, the present invention is not by any means limited to the above embodiments, and it can be applied to various embodiments without departing from the scope of the invention.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. An impeller that is employed for a fuel pump and boosts a pressure of fuel by rotating the fuel in a pump passage, which is formed in the fuel pump in a rotational direction of the impeller, the impeller comprising: a plurality of vane grooves formed adjacent to each other in the rotational direction of the impeller; and a plurality of vanes formed adjacent to each other in the rotational direction of the impeller, wherein: each one of the plurality of vanes divides one of adjacent two of the plurality of vane grooves from the other; and a difference between a maximal value and a minimum value of an adjacent vane angle is set in a range of 2.5° to 4°, wherein the adjacent vane angle is an angle, which is made around a rotational axis of the impeller between respective ends of adjacent two of the plurality of vanes in the rotational direction of the impeller.
 2. The impeller according to claim 1, wherein each adjacent vane angle is set in a range of 8° to 12°.
 3. A fuel pump comprising: a motor unit; the impeller recited in claim 1, wherein the impeller is rotated by rotation driving force of the motor unit; and a casing member that rotatably receives the impeller and defines the pump passage. 